Found this when I logged into my Vonage account:
Vonage is committed to helping during difficult times. In the wake of the recent devastating earthquake in Haiti, Vonage is currently offering free international dialing to Haiti for all U.S. callers. Dial 800-809-2503 and follow the instructions to place a free 10-min call. We encourage you to pass this Vonage toll-free number along to non-Vonage customers who want to call Haiti.
Remember, calls to Haiti are free only if you use this toll-free number to place the call. If you dial from your home phone without using the 800 number, you’ll incur standard long-distance charges. Please note that due to infrastructure limitations in Haiti, you may experience difficulty reaching your party successfully. This free calling service to Haiti may be discontinued at any time.
Please note this is not just for Vonage customers. It's for ALL US callers to Haiti.